If non-nil, `switch-to-buffer' tries to preserve `window-point'.
If this is nil, `switch-to-buffer' displays the buffer at that
buffer's `point'. If this is `already-displayed', it tries to
display the buffer at its previous position in the selected
window, provided the buffer is currently displayed in some other
window on any visible or iconified frame. If this is t, it
unconditionally tries to display the buffer at its previous
position in the selected window.
This variable is ignored if the buffer is already displayed in
the selected window or never appeared in it before, or if
`switch-to-buffer' calls `pop-to-buffer' to display the buffer.